Add 4GB swap and tweak swappiness and vfs cache pressure

add_swap.sh

# create a 4G swap file at /swapfile
sudo fallocate -l 4G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

# Make the Swap File Permanent
sudo echo "/swapfile   none    swap    sw    0   0" >> /etc/fstab

# set swappiness to 10
sudo sysctl vm.swappiness=10
sudo echo "vm.swappiness=10" >> /etc/sysctl.conf

# set vfs_cache_pressure to 50
sudo sysctl vm.vfs_cache_pressure=50
sudo echo "vm.vfs_cache_pressure = 50" >> /etc/sysctl.conf